This invention relates to improvements in a gasket for hermetically seal a clearance between two members.
Hitherto a gasket has been extensively used to be installed in a gasket groove formed in one of two members such as a head cover and a cylinder head of an engine in order to hermetically seal a clearance between the two members. Additionally, a so-called low repulsion-type gasket has been recently extensively used in case that a member having the gasket groove is formed of a relatively low rigidity material such as synthetic resin, as disclosed in Japanese Patent Provisional Publication Nos. 2003-269613, 2004-204941 and 2002-340190. The low repulsion-type gasket is arranged to be suppressed lower in repulsion so as to ensure a certain clearance between a side surface defining the gasket groove and a side surface of the gasket by reducing the width of the gasket in an initial state before compression.
In order to prevent such a low repulsion-type gasket from bucking and meandering, an annular projection is formed at the side surface of the gasket so as to project laterally as disclosed in the above Japanese Patent Provisional Publication Nos. 2003-269613 and 2004-204941. Additionally, in order to improve installation safety and assembly operational efficiency, a flat surface portion formed at the side surface of the gasket is brought into contact with the side surface defining the gasket groove, in a state (before compression of the gasket) where the gasket is inserted and set in the gasket groove.